Image forming apparatus, control method for image forming apparatus, and control program for image forming apparatus

Abstract

To provide an image forming apparatus capable of performing appropriate abnormality handling actions when incorrect paper is stored in the paper feed tray. [Solution] The electrophotographic image forming apparatus 1 according to the present invention comprises a paper feeding unit 2 for feeding paper Sh, a transport unit 37 for transporting paper Sh, an image forming unit 3 for forming an image on the transported paper Sh, a detection unit 41 disposed upstream of the image forming unit 3 for detecting the characteristics of the transported paper Sh, and a control unit 43 that compares the detection characteristics of the transported paper Sh with the reference characteristics of the paper Sh set in the storage unit to determine whether they match, and if they do not match, performs an abnormality handling operation for the transported paper Sh. The control unit 43 changes the content of the abnormality handling operation according to the detection characteristics of the transported paper Sh if they do not match.

Description

Technical Field

[0001] The present disclosure relates to an image forming apparatus, a control method for an image forming apparatus, and a control program for an image forming apparatus.

Background Art

[0002] Conventionally, electrophotographic image forming apparatuses are known. In this type of image forming apparatus, a toner image formed on a photosensitive drum is transferred onto a sheet of paper, and the toner image placed on the paper is fixed by heat and pressure, thereby forming an image on the paper.

[0003] By the way, in this type of image forming apparatus, sheets of paper with various characteristics are used as printing target papers. And in this type of image forming apparatus, usually, in order to produce a printed matter of higher quality, a configuration is adopted in which printing conditions such as the conveyance speed of the paper and the temperature of the fixing roller are set and changed according to the characteristics of the paper.

[0004] In particular, in this type of image forming apparatus, the fixing process conditions in image formation (for example, fixing temperature, fixing roller pressure, fixing speed, etc.) are major factors that affect image quality. For example, in order to sufficiently fix the toner onto the paper, it is necessary to heat not only the toner but also the paper sufficiently. This is because even if the toner melts due to the heat of the fixing roller, sufficient heat cannot be applied to the paper, so sufficient fixing strength cannot be obtained. Therefore, for example, for a paper that is difficult to increase in temperature (for example, a thick paper or a paper with a large basis weight), it is necessary to adjust the fixing process conditions so that a large amount of heat can be obtained during fixing. Also, in a paper with low paper resistance or high smoothness, slippage may occur on the paper during fixing, which may cause image quality degradation. Therefore, when performing a fixing process on such a paper, it is necessary to increase the fixing roller pressure. Also, when the moisture content of the paper is high, the paper is likely to curl. Therefore, when performing a fixing process on such a paper, it is necessary to slow down the fixing speed.

[0005] Given this background, for example, a media sensor for detecting paper characteristics is installed in the image forming apparatus, and the control unit automatically changes the printing conditions according to the paper characteristics detected by the media sensor. See, for example, Patent Document 1. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-009237 [Overview of the project] [Problems that the invention aims to solve]

[0007] Incidentally, in this type of image forming apparatus, due to user misrecognition or other reasons, paper of a different type than that specified in the print job may be stored in the paper tray. In particular, in print jobs that use multiple types of paper to create booklets or the like, such storage errors are likely to occur because each type of paper needs to be stored in a separate paper tray.

[0008] In the following, paper of a different type than the paper type specified in the print job will be referred to as "incorrect paper." Here, "incorrect paper" is paper whose material, thickness, smoothness, moisture content, etc. (hereinafter referred to as "paper characteristics") differ from the paper specified in the print job.

[0009] Therefore, in conventional image forming apparatuses, if a media sensor detects that the paper being transported is incorrect, the main unit is immediately stopped. However, this process causes a jam (i.e., a paper jam) inside the machine, so the user has to remove the paper from inside the machine after the immediate stop in order to clear the jam.

[0010] In recent image forming machines, to eliminate such complications, some are considering a system that, even if a paper being transported is detected to be incorrect, does not immediately stop the machine's operation but instead ejects the paper into a separate purge tray from the normal paper.

[0011] In such abnormality handling operations, when an incorrect sheet of paper is ejected to the purge tray, it is normally ejected by passing through the image forming unit. Therefore, depending on the type of paper (i.e., its characteristics), there is a problem that the incorrect sheet of paper may ignite, melt, or become entangled in the fixing roller during the fixing process, potentially causing internal machine malfunction. If such an internal machine malfunction occurs, internal repair of the image forming unit will be necessary to remove the foreign object, etc.

[0012] This invention has been made in view of the above-mentioned problems. Specifically, the objective is to provide an image forming apparatus, a control method for the image forming apparatus, and a control program for the image forming apparatus that can perform appropriate abnormality handling operations when an incorrect sheet of paper is transported. [Means for solving the problem]

[0013] The main present invention that solves the aforementioned problems is: An electrophotographic image forming apparatus, A transport unit that transports paper, An image forming unit that forms an image on the paper being transported, A detection unit is disposed upstream of the image forming unit and detects the characteristics of the paper being transported, A control unit that performs an abnormality handling operation for the paper being transported when the detection characteristics of the paper being transported satisfy predetermined conditions, Equipped with, The control unit, when the predetermined conditions are met, changes the content of the abnormality handling operation according to the detection characteristics of the paper being transported. It is an image forming apparatus.

[0014] Also, in other situations, A control method for an electrophotographic image forming apparatus, comprising: a first process of conveying a sheet; a second process of performing image formation on the conveyed sheet; a third process of detecting the characteristics of the conveyed sheet on the upstream side of the image forming unit; a fourth process of performing an abnormal situation handling operation on the conveyed sheet when the detected characteristics of the conveyed sheet satisfy a predetermined condition; and in the fourth process, when the predetermined condition is satisfied, the content of the abnormal situation handling operation is changed according to the detected characteristics of the conveyed sheet <00,00073>is a control method.

[0015] In another aspect, a control program for an electrophotographic image forming apparatus, comprising: a first process of conveying a sheet; ] a second process of performing image formation on the conveyed sheet; a third process of detecting the characteristics of the conveyed sheet on the upstream side of the image forming unit; a fourth process of performing an abnormal situation handling operation on the conveyed sheet when the detected characteristics of the conveyed sheet satisfy a predetermined condition; and in the fourth process, when the predetermined condition is satisfied, the content of the abnormal situation handling operation is changed according to the detected characteristics of the conveyed sheet is a control program.

Advantages of the Invention

[0016] According to the image forming apparatus according to the present disclosure, when a misfed sheet is conveyed, it is possible to execute an appropriate abnormal situation handling operation.

Brief Description of the Drawings

[0017] [Figure 1] Schematic diagram showing an overall configuration example of an image forming apparatus according to an embodiment of the present invention <, [Figure 2] Diagram showing a configuration example of a control system of an image forming apparatus according to an embodiment of the present invention [Figure 3] Diagram showing an example configuration of a media sensor related to one embodiment of the present invention. [Figure 4] A diagram showing an example of error paper detection processing related to one embodiment of the present invention. [Figure 5] A diagram showing an example of in-machine fault detection processing related to one embodiment of the present invention. [Figure 6] A flowchart illustrating an example of the operation of the engine control unit according to one embodiment of the present invention. [Figure 7] A flowchart showing a modified example of the operation of the engine control unit according to one embodiment of the present invention. [Figure 8] This figure shows an example of a determination threshold change screen displayed on the operation display unit by the engine control unit in an image forming apparatus according to one embodiment of the present invention. [Modes for carrying out the invention]

[0018] Preferred embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same function are denoted by the same reference numerals, and redundant descriptions will be omitted.

[0019] <Configuration of an image forming apparatus> First, with reference to Figure 1, an example of the configuration of an image forming apparatus according to one embodiment of the present invention (hereinafter referred to as "image forming apparatus 1") will be described.

[0020] Figure 1 is a schematic diagram showing an example of the overall configuration of the image forming apparatus 1.

[0021] The image forming apparatus 1 comprises a paper feeding unit 2, an image forming unit 3, and a post-processing unit 5.

[0022] The paper feeding unit 2 is equipped with three paper feeding trays 21, and supplies (feeds) paper Sh from the paper feeding trays 21. The paper feeding trays 21 are containers that store the paper Sh on which images are formed in the toner image forming unit 30. In the following description, paper Sh will also be referred to as "media". The paper set in the paper feeding trays 21 is fed to the image forming unit 3. The paper feeding unit 2 corresponds to the "paper feeding unit" of the present invention.

[0023] The image forming unit 3 forms an image on paper using an electrophotographic method. For example, the image forming unit 3 forms a color image on the paper Sh by superimposing four toner images of yellow (Y), magenta (M), cyan (C), and black (K) in a tandem format. A PC 6, operated by an operator, is connected to the image forming unit 3 via a LAN (not shown). The image forming unit 3 then performs various processes, such as image forming, according to the jobs submitted from the PC 6 via the LAN.

[0024] The post-processing unit 5 performs predetermined post-processing (also called finisher processing) on ​​the paper Sh whose image has been correctly formed by the image forming unit 3. The post-processing unit 5 is connected to a first output tray 51, a second output tray 52, and a purge tray 53. Paper Sh that has undergone post-processing is output to the first output tray 51. Paper Sh that does not require post-processing is output to the second output tray 52. ​​Paper Sh that has been determined to be erroneous is output to the purge tray 53.

[0025] Here, we will describe an example of the configuration of the image forming unit 3.

[0026] The image forming unit 3 includes an image input unit 11, an operation display unit 13, a toner image forming unit 30, and a transport unit 37.

[0027] The image input unit 11 optically reads an image from a document on the document glass 12, and generates image data (scan data) by performing A / D conversion on the read image. The image input unit 11 can also read from the platen glass provided on the upper surface of the toner image forming unit 30.

[0028] The operation display unit 13 consists of a display unit made of an LCD panel or the like, and an operation unit made of a touch sensor or the like. The display unit and the operation unit are integrally formed, for example, as a touch panel. The operator checks the dialogs and screens displayed on the operation display unit 13. Therefore, the operation display unit 13 is used as a display unit that shows information to the operator informing them that the resumption of job execution has been stopped. The operation display unit 13 is also used as an input unit where the operator inputs instructions to interrupt or execute a job.

[0029] The operation display unit 13 generates an operation signal representing the content of the operation input by the operator and supplies this operation signal to the engine control unit 43 (see Figure 2, described later). The operation display unit 13 also displays the content of the operation performed by the operator, setting information, etc., based on the display signal supplied from the engine control unit 43.

[0030] The transport unit 37 transports the paper Sh fed from the paper feeding unit 2. Specifically, the transport unit 37 first transports the paper Sh from the paper feeding tray 21 to the toner image forming unit 30. Next, the transport unit 37 transports the paper Sh from the toner image forming unit 30 to the post-processing unit 5. Next, the transport unit 37 transports the paper Sh from the post-processing unit 5 to the first paper output tray 51, the second paper output tray 52, or the purge tray 53. The transport unit 37 is composed of, for example, multiple transport rollers, motors that drive these transport rollers, and a rotating member for flipping over paper Sh that has been printed on only one side during double-sided printing.

[0031] The toner image forming unit 30 comprises four toner image forming units 31Y, 31M, 31C, and 31K for forming toner images of Y, M, C, and K colors, and forms an image on paper Sh according to the job. Each toner image forming unit 31Y, 31M, 31C, and 31K comprises a charging unit, an exposure unit (not shown), a photosensitive drum 32Y, 32M, 32C, and 32K as an image carrier, and a developing unit 33Y, 33M, 33C, and 33K, respectively. The toner image forming unit 30 corresponds to the "image forming unit" of the present invention.

[0032] The developing units 33Y, 33M, 33C, and 33K irradiate each surface (outer periphery) of the photosensitive drums 32Y, 32M, 32C, and 32K with light corresponding to the image, thereby forming an electrostatic latent image on the periphery of each photosensitive drum. The developing units 33Y, 33M, 33C, and 33K then develop a toner image on the photosensitive drums 32Y, 32M, 32C, and 32K by depositing toner onto the electrostatic latent image.

[0033] Furthermore, the toner image forming unit 30 includes an intermediate transfer belt 34, a secondary transfer unit 35, and a fixing unit 36. The intermediate transfer belt 34 is a belt on which the toner images formed on the photoreceptor drums 32Y, 32M, 32C, and 32K are primary transferred. The secondary transfer unit 35 is a roller that secondary transfers the toner images of each color primary transferred onto the intermediate transfer belt 34 to the paper Sh that has been transported by the transport unit 37.

[0034] The fixing unit 36 ​​is positioned downstream of the secondary transfer unit 35 in the paper transport direction and performs a fixing process on the paper Sh on which a color toner image has been formed, supplied from the toner image forming unit 30. The fixing unit 36 ​​heats and pressurizes the transported paper Sh to fix the toner image transferred by the toner image forming unit 30 to the surface side of the paper Sh. Printing is completed when the image formed on the paper Sh is fixed in this way.

[0035] The fixing section 36 is composed of, for example, a pair of fixing members, namely an upper fixing roller 36a and a lower fixing roller 36b. The upper fixing roller 36a and the lower fixing roller 36b are arranged in a state of pressure contact with each other, and a fixing nip section is formed as the pressure contact area between the upper fixing roller 36a and the lower fixing roller 36b.

[0036] A heating element (for example, a halogen heater) is provided inside the fixing roller 36a. The roller portion of the fixing roller 36a is heated by radiant heat from this heating element. The heat from the roller portion of the fixing roller 36a is then transferred to the paper Sh, thereby thermally fixing the toner image on the paper Sh.

[0037] The paper Sh is transported so that the side on which the toner image has been transferred by the secondary transfer section 35 (the side to be fixed) faces the upper fixing roller 36a, and passes through the fixing nip section. Therefore, as the paper Sh passes through the fixing nip section, it is subjected to pressure from the upper fixing roller 36a and the lower fixing roller 36b, and is heated by the heat from the roller part of the upper fixing roller 36a.

[0038] Examples of the fixing process conditions for the fixing unit 36 ​​include the temperature of the fixing nip (i.e., fixing temperature), the pressure applied to the fixing nip (i.e., fixing roller pressure), and the speed at which the paper Sh passes through the fixing nip (i.e., fixing speed). The fixing temperature of the fixing unit 36 ​​can be adjusted, for example, by controlling the temperature of the heating element provided inside the fixing upper roller 36a (e.g., by PWM control of the drive power supplied to the halogen heater). The fixing roller pressure of the fixing unit 36 ​​can be adjusted, for example, by variable control of the distance between the fixing upper roller 36a and the fixing lower roller 36b. The fixing speed of the fixing unit 36 ​​can be adjusted, for example, by variable control of the transport speed of the paper Sh in the fixing nip.

[0039] Furthermore, a fixing unit sensor 48 is provided adjacent to the fixing unit 36 ​​to detect the current fixing process conditions (in this case, the fixing temperature) of the fixing unit 36.

[0040] The paper Sh on which the image has been fixed by the fixing unit 36 ​​is transported to the post-processing unit 5 by the transport unit 37. The post-processing unit 5's post-processing unit 50 performs various post-processing operations on the paper Sh on which the image has been formed. These post-processing operations include, for example, at least one of the following: folding the paper Sh, binding the paper Sh, perforating the paper Sh, gluing the paper Sh, and cutting the paper Sh. The post-processed paper Sh is then discharged by the transport unit 37 to either the first output tray 51 or the purge tray 53.

[0041] <Example of Functional Configuration of an Image Forming Apparatus> Figure 2 shows an example of the configuration of the control system of the image forming apparatus 1. Figure 3 shows an example of the configuration of the media sensor 41.

[0042] The paper feeding unit 2 includes a paper feeding control unit 23 that feeds the paper Sh stored in the paper feeding tray 21 to the image forming unit 3. The paper feeding control unit 23 performs the paper feeding operation under the control of the engine control unit 43 of the image forming unit 3.

[0043] The image forming unit 3 includes a media sensor 41, an image processing unit 42, an engine control unit 43, a storage device 44, a printer engine 45, and a fuser unit sensor 48.

[0044] The media sensor 41 is positioned in the transport path of the transport unit 37 upstream of the toner image forming unit 30 and detects the characteristics of the paper Sh fed from the paper feeding unit 2 (see Figure 3).

[0045] The media sensor 41 detects the characteristics of the paper Sh each time it is transported from the paper feed tray 21 to the toner image forming unit 30. In this example, the media sensor 41 detects the thickness, surface roughness, basis weight, moisture content, stiffness, paper resistance, size, transmittance, and reflectance of the paper Sh as paper characteristics. The media sensor 41 corresponds to the "detection unit" of the present invention.

[0046] The media sensor 41 includes a first LED 41a, a first phototransistor 41b, a second LED 41c, a second phototransistor 41d, and a calculation unit 41e, etc.

[0047] The first LED 41a shines light toward the paper Sh, and the first phototransistor 41b receives the light that is shone from the first LED 41a and passes through the paper Sh.

[0048] The calculation unit 41e measures the light transmittance in the paper Sh based on the intensity of the light irradiated by the first LED 41a (irradiated light) and the light received by the first phototransistor 41b (transmitted light). The calculation unit 41e then detects the thickness of the paper Sh based on the transmittance and a predetermined function, for example.

[0049] The second LED 41c shines light toward the paper Sh, and the second phototransistor 41d receives the light that was shone from the second LED 41c and reflected from the paper Sh.

[0050] The calculation unit 41e measures the reflectance of light on the paper Sh based on the intensity of the light irradiated by the second LED 41c (irradiated light) and the light received by the second phototransistor 41d (reflected light). The calculation unit 41e then detects the surface roughness of the paper Sh based on the reflectance and a predetermined function, for example.

[0051] Furthermore, the calculation unit 41e detects the moisture content of the paper Sh from the intensity of scattered light from the paper Sh, for example. Also, the calculation unit 41e detects the basis weight of the paper Sh from the transmittance of the paper Sh, for example.

[0052] The calculation unit 41e notifies the engine control unit 43 of the detected paper characteristics information. However, the engine control unit 43 may determine the paper thickness, surface roughness, basis weight, moisture content, transmittance, and reflectance instead of the calculation unit 41e.

[0053] The fixing unit sensor 48 is a sensor for sensing the fixing process conditions of the fixing unit 36, and is composed of, for example, an infrared sensor or a thermistor to detect the fixing temperature.

[0054] The image processing unit 42, under the control of the engine control unit 43, performs image processing on the image data transferred from the PC 6 and stores the obtained image data in the storage device 44. Examples of image processing performed by the image processing unit 42 include RIP (Raster Image Processor) processing, correction processing, color conversion processing, gradation correction processing, and pseudo-halftone processing.

[0055] The engine control unit 43 provides overall control over each part of the image forming unit 3. For example, the engine control unit 43 controls the toner image forming operation of the toner image forming unit 30 and the transport operation of the transport unit 37.

[0056] The engine control unit 43 comprises a CPU 43a, a ROM 43b, and a RAM 43c. The CPU 43a, ROM 43b, and RAM 43c are each connected to a bus (not shown). The engine control unit 43 communicates with the media sensor 41, the image processing unit 42, and the storage device 44.

[0057] The CPU 43a reads the program code of the control program that implements each function according to this embodiment from the ROM 43b and loads it into the RAM 43c, and executes various controls according to this embodiment. The ROM 43b stores the control program that the CPU 43a reads. In addition to the OS and various parameters, the ROM 43b also records the program for making the engine control unit 43 function. The RAM 43c is used to temporarily store data for executing the control program. Variables and parameters that occur during the calculation process of the CPU 43a are temporarily written to the RAM 43c, and these variables and parameters are read out by the CPU 43a as appropriate.

[0058] In the following, the engine control unit 43 will be abbreviated as "control unit 43".

[0059] The storage device 44 is an example of non-volatile storage and stores various data output from the engine control unit 43. Examples of storage devices 44 include HDDs, SSDs, or non-volatile memory. The CPU 43a may also read and execute programs stored in the storage device 44.

[0060] The post-processing unit 5 includes a finisher control unit 55. The finisher control unit 55 controls various post-processing (finisher processing) performed in the post-processing unit 50.

[0061] <Detailed configuration of the engine control unit 43> The control unit 43 has an error paper detection function and an abnormality handling action determination function to deal with cases where incorrect paper is stored in the paper tray 21 due to user misidentification or the like. The error paper detection function determines whether the paper Sh being transported by the transport unit 37 is "error paper". The abnormality handling action determination function determines the content of the abnormality handling action to be taken for the paper Sh being transported if it is "error paper".

[0062] First, let me explain the error detection function.

[0063] When a print job is performed, the memory unit (for example, RAM 43c) of the control unit 43 is initially set with the print conditions and the reference characteristics of the paper Sh used for printing, thereby forming the print job data.

[0064] Printing conditions include, for example, the transport speed by the transport unit 37 and the fixing process conditions by the fixing unit 36 ​​(e.g., fixing temperature and fixing roller pressure). Furthermore, the reference characteristics of the paper Sh are, for example, the same as the items detected by the media sensor 41, such as the thickness, surface roughness, basis weight, moisture content, transmittance, and reflectance of the paper Sh. These printing conditions and reference characteristics of the paper Sh can be set, for example, by the user selecting from candidate items using the operation display unit 13 when creating a print job.

[0065] When a print job is started, the control unit 43 acquires the detection result of the characteristic value of the paper Sh from the media sensor 41 (hereinafter referred to as "detection characteristic") each time a sheet of paper Sh is transported. The control unit 43 then compares the detection characteristic of the paper Sh being transported by the transport unit 37 with the reference characteristic of the specified paper set in the storage unit (for example, RAM 43c) and determines whether the two match. Based on this, the control unit 43 determines whether the paper being transported is an "error paper".

[0066] The control unit 43 compares the detection characteristics of the paper Sh with the reference characteristics of a specified paper set in the memory unit (e.g., RAM 43c) for each item, such as thickness, surface roughness, basis weight, moisture content, stiffness, paper resistance, size, transmittance, and reflectance, and determines their identity. The control unit 43 determines that the paper Sh being transported is "normal paper" if the degree of agreement between the detection characteristics of the paper Sh and the reference characteristics is below a threshold for each item. On the other hand, the control unit 43 determines that the paper Sh being transported is "incorrect paper" if the degree of agreement for even one item is above the threshold. Note that the characteristic items to be compared may be limited to only the main items useful for determining the type of paper. For example, the characteristic items to be compared may be limited to transmittance and reflectance.

[0067] Figure 4 shows an example of the error paper detection process. In Figure 4, transmittance and reflectance are set as the determination thresholds for error paper detection. The control unit 43 virtualizes a two-dimensional coordinate system, for example, as shown in Figure 4, where the X coordinate is reflectance and the Y coordinate is transmittance. The control unit 43 then calculates the distance Dk between the coordinates of the reference characteristics of the specified paper (Rx1, Ry1) and the coordinates of the detection characteristics of the paper Sh being transported (Rx2, Ry2) in this two-dimensional coordinate system. The control unit 43 determines that if the distance Dk is less than the first threshold TH1, the paper Sh being transported matches the specified paper. On the other hand, if the distance Dk is greater than or equal to the first threshold TH1, the control unit 43 determines that the paper Sh being transported does not match the specified paper (i.e., it is an error paper). The first threshold TH1 is stored in the storage device 44 beforehand, for example.

[0068] Next, I will explain the function for determining the correct action to take in case of an anomaly.

[0069] As described above, if a sheet of paper Sh being transported is found to be an incorrect sheet, it is necessary to prevent that sheet from being mixed with normal printed materials. In this regard, a method used in conventional image forming apparatuses, which immediately stops the operation of the main unit when it is determined that a sheet of paper being transported is an incorrect sheet, will cause a jam (i.e., a paper jam) inside the machine.

[0070] On the other hand, if a sheet of paper Sh being transported is determined to be an incorrect sheet of paper, uniformly ejecting that sheet of paper Sh into the purge tray 53 may cause an internal malfunction at the location of the toner image forming unit 30.

[0071] Therefore, in this embodiment, if the control unit 43 determines that the paper Sh being transported is an incorrect sheet of paper, it changes the content of the abnormality handling operation according to the detection characteristics of the paper Sh being transported. Specifically, the control unit 43 makes a determination regarding whether or not an in-machine malfunction has occurred based on the detection characteristics of the paper Sh being transported. If an in-machine malfunction is expected, the control unit 43 performs an abnormality handling operation to immediately stop the operation of the transport unit 37 and the toner image forming unit 30 before the paper Sh being transported passes through the toner image forming unit 30. Alternatively, it performs an operation to eject the incorrect paper Sh being transported into a purge tray 54 (not shown) provided before it passes through the toner image forming unit 30. The purge tray 54 is, for example, a purge tray located between the paper feed unit 2 and the toner image forming unit 30. On the other hand, if an in-machine malfunction is not expected, the control unit 43 performs an abnormality handling operation to eject the incorrect paper Sh being transported into the purge tray 53.

[0072] In this context, "machine malfunction" refers to situations such as paper Sh igniting, melting, or becoming entangled in the fixing roller during the toner image forming unit 30 while being transported.

[0073] This abnormality handling action determination function makes it possible to suppress the occurrence of situations where erroneous paper ignites or melts while passing through the toner image forming unit 30, while also avoiding the hassle of the erroneous paper unnecessarily causing jams in the machine.

[0074] Figure 5 shows an example of the in-flight fault detection process.

[0075] Figure 5 shows an example where the thickness of the paper Sh is used as a threshold for determining in-machine malfunction. The reason why incorrect paper may ignite or melt while passing through the toner image forming unit 30 is that, under the fixing process conditions in the toner image forming unit 30 set based on the standard characteristics of the specified paper, the incorrect paper cannot withstand the heat it receives in the fixing unit 36. In other words, the incorrect paper becomes overheated due to the heat it receives in the fixing unit 36. In this respect, the thickness of the paper is an effective indicator for simply evaluating the heat resistance of the paper.

[0076] Therefore, the control unit 43 according to this embodiment determines whether or not an in-machine malfunction occurs based on the detected thickness of the paper Sh being transported and the fixing temperature in the toner image forming unit 30, which is set based on the reference characteristics of the specified paper.

[0077] In this embodiment, as an example, a failure threshold data table is used in which a second threshold TH2 related to the paper thickness is set as a determination threshold for in-machine failure detection, which is pre-stored in the storage device 44. In this failure threshold data table, for each fixing temperature in the fixing unit 36, a second threshold TH2 related to the paper thickness is set in association with that fixing temperature.

[0078] Specifically, the control unit 43 plots, for example, the fixing temperature Ta1, which is set based on the reference characteristics of the specified paper, and the detected paper thickness Ta2 of Sh, on the graph shown in Figure 5, as points to be judged. That is, it compares the detected paper thickness Ta2 of Sh with the thickness of the second threshold TH2 set in the failure threshold data table. The control unit 43 then determines that if the point to be judged is in the region above the second threshold TH2, an in-machine failure is not expected. On the other hand, the control unit 43 determines that if the point to be judged is in the region below the second threshold TH2, an in-machine failure is expected.

[0079] However, the determination method shown in Figure 5 is just one example, and the in-machine fault determination process can be modified in various ways. For example, the detection characteristics of the paper Sh to be determined may not be limited to the thickness of the paper Sh, but may also refer to the basis weight of the paper Sh, etc. Also, instead of using the thickness of the paper Sh itself as an indicator, the transmittance and reflectance that are referenced when calculating the thickness of the paper Sh may be referenced. On the other hand, the fixing process conditions that serve as indicators when setting the comparison target may also refer to fixing pressure and transport speed, in addition to the fixing temperature in the fixing unit 36.

[0080] <Operation flow of the engine control unit 43> The following describes an example of the operation flow of the control unit 43 according to this embodiment.

[0081] Figure 6 is a flowchart showing an example of the operation of the control unit 43. Here, only the operations related to the error paper detection function and the abnormality handling action determination function performed by the control unit 43 to deal with the case when incorrect paper is stored in the paper tray 21 will be explained.

[0082] In step S1, when a print job is input to the image forming apparatus 1, the control unit 43 first sets the print conditions specified in the print job and the reference characteristics of the paper Sh in the storage unit (for example, RAM 43c). The reference characteristics of the paper Sh are automatically set from a paper reference characteristics data table stored in the storage device 44 in advance, based on the identification information of the paper Sh specified in the print job.

[0083] In step S2, the control unit 43 causes the paper feed unit 2 to feed the paper Sh specified in the print job, and the transport unit 37 transports the paper Sh.

[0084] In step S3, the control unit 43 detects the characteristics of the paper Sh being transported using the media sensor 41. Here, for example, the control unit 43 detects the thickness, surface roughness, basis weight, moisture content, stiffness, paper resistance, size, transmittance, and reflectance of the paper Sh being transported using the media sensor 41.

[0085] In step S4, the control unit 43 compares the characteristics of the detected paper Sh with the reference characteristics of paper Sh set in the storage unit and determines whether they match. If they match (S4: YES), the control unit 43 determines that "the paper Sh being transported is not an error paper" and proceeds to step S5. On the other hand, if they do not match (S4: NO), the control unit 43 determines that "the paper Sh being transported is an error paper" and proceeds to step S6.

[0086] Furthermore, in step S4, the control unit 43 performs a paper error determination by comparing the detected transmittance and reflectance of the paper Sh with the transmittance and reflectance of the paper Sh set in the memory unit as reference characteristics, for example, as shown in Figure 4.

[0087] In step S5, the control unit 43 instructs the toner image forming unit 30 to perform a printing operation on the paper Sh being transported. After printing on the paper Sh, the control unit 43 ejects the paper Sh to either the first paper output tray 51 or the second paper output tray 52. ​​At this time, if the paper Sh requires post-processing, the control unit 43 performs post-processing in the post-processing unit 5 before ejecting it to the first paper output tray 51. On the other hand, if the paper Sh does not require post-processing, it is ejected to the second paper output tray 52 without post-processing in the post-processing unit 5.

[0088] In step S6, the control unit 43 determines whether an in-machine malfunction will occur if the transported paper Sh (error paper) passes through the toner image forming unit 30. Here, the control unit 43 determines whether an in-machine malfunction will occur based on whether the detection characteristics (in this case, the detection thickness) of the transported paper Sh (error paper) are greater than or equal to the second threshold TH2. If the detection characteristics of the transported paper Sh are less than the second threshold TH2 (S6: YES), the control unit 43 determines that an in-machine malfunction will occur and proceeds to step S7. On the other hand, if the detection characteristics of the transported paper Sh are greater than or equal to the second threshold TH2 (S6: NO), the control unit 43 determines that an in-machine malfunction will not occur and proceeds to step S8.

[0089] In step S6, the control unit 43, for example as shown in Figure 5, identifies a second threshold TH2 related to the thickness set in the failure threshold data table from the fixing temperature in the toner image forming unit 30, which is set based on the reference characteristics of the specified paper. Then, by comparing this second threshold TH2 with the detected thickness of the paper Sh being transported, it determines whether or not an in-machine failure occurs.

[0090] In step S7, the control unit 43 immediately stops the transport unit 37 and the toner image forming unit 30, stopping the print job before the transported paper Sh reaches the toner image forming unit 30 (particularly the fuser unit 36). This prevents the transported paper Sh from causing an in-machine malfunction.

[0091] In step S8, the control unit 43 ejects the paper Sh being transported into the purge tray 53 without immediately stopping the transport unit 37 and the toner image forming unit 30. In this case, since there is no risk of the transported paper Sh causing an in-machine malfunction, the transported paper Sh is allowed to pass through the toner image forming unit 30 and be ejected to the purge tray 53. In other words, this avoids causing a jam in the machine by immediately stopping it.

[0092] In the image forming apparatus 1 according to this embodiment, even if the wrong paper is stored in the paper feed tray 21, the process described above can suppress the occurrence of internal machine malfunctions and allow the transported paper Sh to be ejected into the purge tray 53.

[0093] [effect] As described above, in this embodiment, An electrophotographic image forming apparatus, A transport unit that transports paper, An image forming unit that forms an image on the paper being transported, A detection unit is disposed upstream of the image forming unit and detects the characteristics of the paper being transported, A control unit that performs an abnormality handling operation for the paper being transported when the detection characteristics of the paper being transported satisfy predetermined conditions, Equipped with, The control unit, when the predetermined conditions are met, changes the content of the abnormality handling operation according to the detection characteristics of the paper being transported. An image forming apparatus was disclosed.

[0094] According to the image forming apparatus of this embodiment, in the event that incorrect paper is stored in the paper feed tray, it is possible to eject the paper being transported into the purge tray while suppressing the occurrence of internal machine malfunctions.

[0095] <Example 1> In the above embodiment, the user sets the reference characteristics of the paper Sh. In this modified example, the paper characteristics detected for the first sheet of paper Sh when the print job is started are used as the reference characteristics of the paper Sh.

[0096] Specifically, in this modified example, the control unit 43 detects the characteristics of the first sheet of paper Sh when the print job is started using the media sensor 41, and then sets the characteristics of the paper Sh detected at this time as a reference characteristic in the storage unit (for example, RAM 43c). Then, when determining errors in the second and subsequent sheets of paper Sh of the print job, the control unit 43 refers to the value of the reference characteristic of the first sheet of paper Sh set in the storage unit.

[0097] The image forming apparatus 1 according to this modified example is useful to the user because it eliminates the need to set the reference characteristics of the paper Sh.

[0098] However, it should be noted that with this configuration, it becomes difficult to handle cases where multiple types of paper Sh are stored in the same paper tray 21.

[0099] <Modification 2> In the above embodiment, the abnormal handling operation for incorrect paper Sh was shown to switch between immediately stopping or ejecting the paper to the purge tray 53, depending on the detection characteristics of the incorrect paper Sh. In this modified example, the abnormal handling operation for incorrect paper Sh is performed to switch the printing conditions of the toner image forming unit 30 according to the detection characteristics of the incorrect paper Sh. That is, in this modified example, for example, all of the incorrect paper Sh may be ejected to the purge tray 53.

[0100] Figure 7 is a flowchart showing a modified example of the operation of the control unit 43.

[0101] The flowchart processing in this modified example is the same as the flowchart processing in Figure 6, except for the processing in S7a. Specifically, in the processing of S4, if an erroneous sheet of paper Sh is detected, the control unit 43 determines whether or not an in-machine malfunction will occur if the erroneous sheet of paper Sh, which is being transported, passes through the toner image forming unit 30. For example, the control unit 43 determines whether or not the detected thickness of the erroneous sheet of paper Sh, which is being transported, is less than the second threshold TH2 (see Figure 5). Here, the second threshold TH2 is referenced from a malfunction threshold data table stored in advance in the storage unit (for example, the storage device 44). That is, the second threshold TH2 is set based on the fixing temperature of the fixing unit 36, which is set based on the reference characteristics of the specified paper in the print job.

[0102] Specifically, if the detected thickness of the paper Sh being transported is less than the second threshold TH2 (S6: YES), the control unit 43 determines that "if the erroneous paper Sh passes through the toner image forming unit 30, an in-machine malfunction will occur," and proceeds to step S7a.

[0103] On the other hand, if the detected thickness of the paper Sh being transported is greater than or equal to the second threshold TH2 (S6:NO), the control unit 43 determines that "it is not a problem to let the erroneous paper Sh pass through the toner image forming unit 30" and proceeds to step S8a.

[0104] In step S7a, the control unit 43 modifies the printing conditions of the toner image forming unit 30 so that the erroneous paper Sh does not ignite or melt while being transported, and then passes the erroneous paper Sh through the toner image forming unit 30 and discharges it to the purge tray 53. Specifically, the control unit 43 lowers the fixing temperature of the fixing unit 36 ​​to a predetermined temperature (for example, the temperature at which a failure occurs corresponding to the detected thickness of the paper Sh identified from the failure threshold data table).

[0105] Furthermore, in step S7a, the control unit 43 may reduce the transport speed of the transport unit 37 in order to extend the time until the erroneous paper Sh reaches the fixing unit 36. This suppresses the erroneous paper Sh from igniting or melting.

[0106] In step S8a, the control unit 43 allows the erroneous paper Sh to pass through the toner image forming unit 30 and discharges it to the purge tray 53 without changing the printing conditions of the toner image forming unit 30 (i.e., the fixing conditions of the fixing unit 36).

[0107] According to the modified image forming apparatus 1, it is possible to eject erroneous paper Sh from the machine without leaving any inside. The modified image forming apparatus 1 is useful to the user because it eliminates the need to deal with jams that occur inside the machine.

[0108] However, it should be noted that with such a configuration, under high-speed printing conditions, it is often difficult, due to time constraints, to change the printing conditions of the toner image forming unit 30 to prevent erroneous paper Sh from igniting or melting during transport.

[0109] <Variation 3> In the image forming apparatus 1 according to the above embodiment, a method is shown in which it is determined whether or not an incorrect sheet of paper Sh causes an in-machine malfunction based on whether or not the detection characteristics of the incorrect sheet of paper Sh (for example, the detection thickness) are greater than or equal to a second threshold TH2.

[0110] The image forming apparatus 1 according to this modified example differs from the above embodiment in that the second threshold TH2 can be changed by the user. That is, the content of the abnormal handling operation for erroneous paper Sh is changed by the second threshold TH2. Therefore, some users may want to change the setting of the second threshold TH2 considering their own usage of the image forming apparatus 1.

[0111] Figure 8 shows an example of a judgment threshold change screen displayed on the operation display unit 13 by the control unit 43 according to this modified example.

[0112] In Figure 8, the user can select the margin level of the second threshold TH2, which determines whether an erroneous sheet of paper Sh will cause an in-machine malfunction, using the pull-down button M1a. Here, for example, "Level 1 (small margin)", "Level 2 (medium margin)", and "Level 3 (large margin)" can be selected as margin levels. In "Level 1 (small margin)", the second threshold TH2 is set to the value at which the detection characteristics of the erroneous sheet of paper Sh (e.g., detection thickness) could potentially cause an in-machine malfunction such as ignition. In "Level 2 (medium margin)", the second threshold TH2 is set to a more lenient value than in "Level 1 (small margin)". In "Level 3 (large margin)", the second threshold TH2 is set to a more lenient value than in "Level 2 (medium margin)". In other words, when "Level 1 (small margin)" is selected, the number of cases in which erroneous sheet of paper Sh is ejected into the purge tray 53 can be increased compared to when "Level 3 (large margin)" is selected.

[0113] Thus, the image forming apparatus 1 according to this modified example is useful in that the threshold for fault detection related to erroneous paper Sh can be changed by the user.

[0114] <Modification 4> In the above embodiment, the description assumed a printing job using only one type of paper Sh, such as a flyer. However, in actual use of the image forming apparatus 1, there are also printing jobs that use multiple types of paper Sh, such as booklets.

[0115] For print jobs using multiple types of paper, such as booklets, each type of paper is stored in a separate paper tray. Standard characteristics and printing conditions are then set for each type of paper.

[0116] In the image forming apparatus 1 according to this modified example, the control unit 43 selects the reference characteristics of the paper Sh to be referenced based on the printing progress during the print job (for example, the number of printed sheets). The control unit 43 then compares the detection characteristics of the paper Sh being transported with the reference characteristics of the paper Sh to determine whether they match. For example, when the k-th sheet of paper Sh is being transported by the transport unit 37, the control unit 43 compares the characteristics of the k-th sheet of paper Sh with the characteristics of the specified paper to determine the identity between the characteristics of the k-th sheet of paper Sh and the characteristics of the specified paper.

[0117] Thus, according to the modified image forming apparatus 1, even when performing a print job using multiple types of paper Sh, it is possible to suppress the occurrence of in-machine malfunctions and eject erroneous paper being transported into the purge tray.

[0118] <Modification 5> In the above embodiment, when an internal malfunction is expected, the operation of the transport unit 37 and the toner image forming unit 30 is immediately stopped as an emergency response operation before the transported paper Sh passes through the toner image forming unit 30.

[0119] However, depending on the model of the image forming apparatus 1, a second purge tray 54 (not shown) may be provided, branching off from the transport path before passing through the toner image forming unit 30. In such an image forming apparatus 1, if there is a risk that an incorrect sheet of paper Sh may cause an in-machine malfunction, the control unit 43 may perform an abnormality response operation, which is to eject the incorrect sheet of paper Sh that is being transported into the second purge tray 54. The second purge tray 54 is, for example, a purge tray provided so as to branch off from a position between the paper feeding unit 2 and the toner image forming unit 30 in the transport path.

[0120] This method also makes it possible to reliably prevent in-machine malfunctions caused by incorrect paper (Sh).

[0121] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. [Industrial applicability]

[0122] According to the image forming apparatus described herein, it is possible to perform appropriate abnormality handling operations when incorrect paper is stored in the paper feed tray. [Explanation of Symbols]

[0123] 1. Image forming apparatus 2 Paper feed unit 3 Image forming unit 5. Post-processing unit 11 Image Input Section 12 Manuscript stand 13 Operation display section 21 Paper feed tray 23 Paper feed control unit 30 Toner image forming section 34 Intermediate transfer belt 35 Secondary transfer section 36 Fixing section 37 Conveying Section 41 Media Sensors 41a First LED 41b First phototransistor 41c 2nd LED 41d Second phototransistor 41e Arithmetic unit 42 Image Processing Unit 43 Engine Control Unit 44 Storage device 45 Printer Engine 48 Fixing Unit Detector 50 Post-processing 51 First paper output tray 52 Second paper output tray 53 Purge Tray 55 Finisher Control Unit Sh Paper

Claims

1. An electrophotographic image forming apparatus, A transport unit that transports paper, An image forming unit that forms an image on the paper being transported, A detection unit is disposed upstream of the image forming unit and detects the characteristics of the paper being transported, A control unit that performs an abnormality handling operation for the paper being transported when the detection characteristics of the paper being transported satisfy predetermined conditions, Equipped with, The control unit, when the predetermined conditions are met, changes the content of the abnormality handling operation according to the detection characteristics of the paper being transported. Image forming apparatus.

2. The control unit compares the detection characteristics of the paper being transported with the reference characteristics of the paper set in the storage unit, and determines that the predetermined conditions are met if the two do not match. The image forming apparatus according to claim 1.

3. The control unit, when the predetermined conditions are met, Based on the detection characteristics of the paper being transported, a determination is made regarding whether or not an in-machine malfunction has occurred due to the paper being transported. If the above-mentioned in-machine malfunction is anticipated, the above-mentioned abnormality response action will be performed to immediately stop the operation of the transport unit and the image forming unit. If the aforementioned machine malfunction is not expected, the abnormality response operation will be to eject the paper being transported into a purge tray located downstream of the image forming unit. The image forming apparatus according to claim 1.

4. The control unit, when the predetermined conditions are met, Based on the detection characteristics of the paper being transported, a determination is made regarding whether or not an in-machine malfunction has occurred due to the paper being transported. If the aforementioned machine malfunction is anticipated, the aforementioned abnormality response operation will be performed to eject the paper being transported into a purge tray located in front of the image forming unit. If the aforementioned machine malfunction is not expected, the abnormality response operation will be to eject the paper being transported into a purge tray located downstream of the image forming unit. The image forming apparatus according to claim 1.

5. The control unit changes the determination threshold for determining whether or not an in-machine malfunction has occurred, based on the fixing process conditions in the image forming unit, which are set based on the reference characteristics of the paper. The image forming apparatus according to claim 2.

6. The determination of whether or not a malfunction has occurred in the machine includes a threshold determination related to the thickness of the detection characteristics of the paper being transported. The image forming apparatus according to claim 2.

7. The aforementioned machine malfunction includes ignition, melting, or jamming of the paper at the fixing roller of the image forming unit while the paper is being transported. The image forming apparatus according to claim 2.

8. If the predetermined conditions are met, the control unit performs a determination based on the detection characteristics of the paper being transported to determine whether or not an in-machine malfunction has occurred due to the paper being transported. If the aforementioned machine malfunction is not expected, as the abnormality response operation, the paper being transported is ejected to a purge tray located downstream of the image forming unit without changing the fixing process conditions in the image forming unit. If the aforementioned machine malfunction is anticipated, the following abnormality response action will be taken: the fixing process conditions will be relaxed, and the paper being transported will be ejected into the purge tray. The image forming apparatus according to claim 1.

9. The system further includes a setting unit that allows the user to change the criteria for determining when modifying the content of the abnormality handling operation. The image forming apparatus according to claim 1.

10. The paper characteristics initially set in the print job data are used as the reference characteristics for the aforementioned paper. The image forming apparatus according to claim 1.

11. The reference characteristics of the paper are set to the characteristics of the paper detected by the detection unit at the beginning of the print job. The image forming apparatus according to claim 1.

12. When the print job consists of multiple pages of different types of paper, the reference characteristics of the paper are set in the storage unit for each type of paper. The control unit selects the reference characteristics of the paper to be referenced based on the printing progress during the print job, and then compares the detection characteristics of the paper being transported with the reference characteristics of the paper to determine whether they match. The image forming apparatus according to claim 2.

13. A control method for an electrophotographic image forming apparatus, The first process involves transporting the paper, A second process in which an image is formed on the paper being transported, Upstream of the image forming unit, a third process is performed to detect the characteristics of the paper being transported, If the detection characteristics of the paper being transported satisfy predetermined conditions, a fourth process is performed to carry out an abnormality handling operation for the paper being transported. Perform In the fourth process, if the predetermined conditions are met, the content of the abnormality handling operation is changed according to the detection characteristics of the paper being transported. Control method.

14. A control program for an electrophotographic image forming apparatus, The first process involves transporting the paper, A second process in which an image is formed on the paper being transported, Upstream of the image forming unit, a third process is performed to detect the characteristics of the paper being transported, If the detection characteristics of the paper being transported satisfy predetermined conditions, a fourth process is performed to carry out an abnormality handling operation for the paper being transported. It has, In the fourth process, if the predetermined conditions are met, the content of the abnormality handling operation is changed according to the detection characteristics of the paper being transported. Control program.

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